Prerequisites for SNMP IfIndex Persistence

None.

Restrictions for SNMP IfIndex Persistence

None.

Information About SNMP IfIndex Persistence

The SNMP ifIndex persistence feature provides an interface index (ifIndex) value that is retained and used when the switch reboots. The ifIndex value is a unique identifying number associated with a physical or logical interface.

There is no requirement in the relevant RFCs that the correspondence between particular ifIndex values and their interfaces be maintained when the switch reboots, but many applications (for example, device inventory, billing, and fault detection) require maintenance of this correspondence.

You can poll the switch at regular intervals to correlate the interfaces to the ifIndexes, but it is not practical to poll constantly. The SNMP ifIndex persistence feature provides permanent ifIndex values, which eliminates the need to poll interfaces.

The following definitions are based on RFC 2233, "The Interfaces Group MIB using SMIv2." The following terms are values in the Interfaces MIB (IF-MIB):

•ifIndex —A unique number (greater than zero) that identifies each interface for SNMP identification of that interface.

•ifName—The text-based name of the interface, for example, "ethernet 3/1."

•ifDescr—A description of the interface. Recommended information for this description includes the name of the manufacturer, the product name, and the version of the interface hardware and software.

Note The [no] snmp ifindex persistence interface commandcannot be used on subinterfaces. A command applied to an interface is automatically applied to all the subinterfaces associated with that interface.

In the following example, SNMP ifIndex persistence is enabled for Ethernet interface 3/1 only:

router(config)# interface ethernet 3/1

router(config-if)# snmp ifindex persist

router(config-if)# exit

In the following example, SNMP ifIndex persistence is disabled for Ethernet interface 3/1 only:

To clear the interface-specific SNMP ifIndex persistence setting and configure the interface to use the global configuration setting, perform this task:

Command

Purpose

Step 1

Router(config)# interfacetype slot/port

Enters interface configuration mode for the specified interface. Note that the syntax of the interface command will vary depending on the platform you are using.

Step 2

Router(config-if)# snmp ifindex clear

Clears any interface-specific SNMP ifIndex persistence configuration for the specified interface and returns to the global configuration setting.

Step 3

Router(config-if)#exit

Exits interface configuration mode.

In the following example, any previous setting for SNMP ifIndex persistence on Ethernet interface 3/1 is removed from the configuration. If SNMP ifIndex persistence is globally enabled, SNMP ifIndex persistence will be enabled for Ethernet interface 3/1. If SNMP ifIndex persistence is globally disabled, SNMP ifIndex persistence will be disabled for Ethernet interface 3/1.

router(config)# interface ethernet 3/1

router(config-if)# snmp ifindex clear

router(config-if)# exit

Tip For additional information about Cisco Catalyst 6500 Series Switches (including configuration examples and troubleshooting information), see the documents listed on this page: